Not Applicable
Not Applicable
The invention herein relates to a motor vehicle steering column switch comprising at least one wiper/washer switch being an integral part of a switch lever, where the switch hasxe2x80x94located on a rotary switch memberxe2x80x94a contact bridge with several contact arms acting on switch contact paths with associated connection contacts.
Known steering column switches of this type have at least one switch for the front or windshield wiping functions, which, in most cases, is located in a rotation-symmetrical manner on a longitudinal axis of a switch lever of the steering column switch and which can lock in different switch positions. A pushbutton switch for a front washing function is in a typical arrangement located on the free end of the switch lever. Frequently, the switch for the front wiping, functions located on the switch lever is associated with another switch for the rear wiping/washing functions. The switch for the front wiping functions, as well as the switch for the rear wiping/washing functions, comprises a number of contact bridges which correspond to the number of switch positions and act on respectively corresponding switch contact paths. These contact bridges, as well as their associated switch contact paths, extend in the form of a segment of a circle relative to the periphery of the rotary switch member of the respective switch on one end of the rotary switch member. Inasmuch as the contact bridges require a relatively large space, the number of switch positions of each switch is limited. In order to enable the front washing function the corresponding pushbutton switch is pressed, whereby the switch actsxe2x80x94via an actuation pushrod associated with a contact bridgexe2x80x94on the respective switch contact paths. The connection of the switch contact paths with the on-board electrical system of the motor vehicle is created by connection lines that are affixed to connection contacts and passed through the longitudinal axis of the steering column switch. The number of connection lines corresponds to at least the number of switch contact paths. The total number of switch positions and hence switch signals, in the switch for the front wiping functions, is greatly restricted due to the space requirements of the respective switch contact paths and their connection lines.
Furthermore, a Gray code has been known as being a particular expression of the binary code. Its basis is that two adjacent Gray numbers do not differ by more than one bit. Inasmuch as the difference between adjacent numbers can only be one digit, it can be recognized reliably during data transfer.
The problem to be solved by the present invention is to provide a steering column switch of the above-described type, which has a wiper/washer switch with a large number of switch positions requiring only a small amount of space, offers high switching reliability and which has a reduced number of connection contacts relative to the switch positions.
In accordance with the present invention this problem has been solved in that the contact bridge and the switch contact paths act together for the transfer of switch function data in Gray code.
This interaction in Gray code, i.e., binary code, results in a reduced number of switch contact paths, as well as contact arms for the contact bridge, compared with the number of switch positions of the wiper/washer switch, thereby resulting in reduced space requirements within the wiper/washer switch and thus in a more compact design of the switch lever while, providing a multitude of switch positions. The reduced number of switch path contacts also means a reduced number of connection contacts and thus a reduced number of connection lines for the connection of these switch contact paths with the on-board electrical system of the motor vehicle. The type of coding, i.e., that two adjacent Gray-coded switch positions do not differ by more than one bit, which can be determined easily, ensures highly reliable switching operations. Therefore, when one switching function is performed, the subsequent one can be identified clearly.
In accordance with an advantageous modification of the invention, a front wiper/washer switch and a rear wiper/washer switch are provided. In this case the different switch functions are associated with the steering wheel switch in a spatially separated manner and can be assembled as needed.
In order to be able to manufacture the contact bridges of both switches at the lowest possible cost the contact bridges of the front and the rear wiper/washer switches are respectively configured as a stamped grid with resilient contact arms. Preferably, the contact arm associated with the front washing function of the contact bridge of the front wiper/washer switch points in a direction opposite the contact arms for the front wiping functions. This permits a reliable actuation of the contact arm associated with the front washing function.
Advantageously, the respective switch contact paths of the front and the rear wiper/washer switches are configured as a stamped grids. Therefore, a reliable contact of the contact bridge respectively associated with one stamped grid can be effected by means of a cost-effective manufacturing process.
In order to achieve a highly efficient assembly during the wiring operation of the steering column switch, the switch contact paths for contact with connection lines are advantageously provided with clamp-and-notch type connections.
Furthermore, the switch contact paths of the front wiper/washer switch are set in a non-rotational spacer ring located between the two rotary handles of the front and the rear wiper/washer switches. Inasmuch as the spacer ring typically consists of plastic material, the switch contact paths are set in by extrusion-coating with the use of an extrusion process.
In accordance with another embodiment of the present invention, a concentric shaft holding the front and rear wiper/washer switches is molded to the spacer ring, and the shaft is held in position by means of the rotary handle of the front wiper/washer switch on one side and in a base of the switch lever on the other side. The two wiper/washer switches are centered relative to each other and additional assembly components are therefore unnecessary.
Preferably, the switch contact paths of the rear wiper/washer switch are mounted to a support located between the base of the switch lever and the rotary handle of the rear wiper/washer switch. This gives the switch contact paths sufficient strength, thereby making them resistant to inadvertent damage. Preferably, this support is located in a non-rotational manner on the spacer ring shaft.
In accordance with another advantageous modification of the present invention, the contact arm of the contact bridge of the rotary switch member of the front wiper/washer switch can be actuated by means of a pushbutton set into the end of the switch lever, thereby actuating a pushrod for the front washing function. Therefore, a separate contact bridge for enabling this switch function is not necessary.
For reliable and secure switch positioning, the rotary switch member of the front wiper/washer switch comprises an end stop which interacts with a spring-biased stop sleeve associated with the spacer ring. Furthermore, the rotary switch member of the rear wiper/washer switch comprises a peripheral stop which interacts with a spring-biased stop sleeve associated with the support. These stops are arranged in a space-saving manner and symmetrically to the longitudinal axis of the steering column switch.